Phosphorus requirements of St. Augustinegrass grown in sandy soils

Phosphorus fertilization of St. Augustinegrass [Stenotaphrum secondatum (Walt.) Kuntze] is performed on the basis of soil tests designed for agronomic crops. The objectives of this study were to determine the critical minimum P application rate and soil and tissue P concentration of St. Augustinegrass grown in sandy soils. Three studies were conducted in a glasshouse using a Pomona sand, two Tavares sands, and a Pottsburg sand. Established pots of 'Floratam' St. Augustinegrass received P at 0, 0.14, 0.27, 0.54, and 1.09 g m(-2) every four weeks for 16 weeks for Study 1 and 12 weeks for Studies 2 and 3. Critical minimum tissue P concentration was determined to be 1.8 g kg(-1) on dry weight basis. Minimum P application rate was 0.14 g m(-2) 4-wk(-1) to obtain acceptable turfgrass quality and growth rate. Additional growth was not observed when Mehlich-1 P level was greater than 7, 8, 9, and 5 mg kg(-1) for Pomona sand, Tavares sand (a), Pottsburg sand, and Tavares sand (b), respectively. Phosphorus fertilization would not be recommended if soil Mehlich-1 P concentration is above 10 mg kg(-1) for sandy soils or tissue P level is beyond 1.8 g kg(-1) on dry weight basis. Phosphorus application of 0.14 g m(-2) 4-wk(-1) is recommended when P is required.